The benefits of unfractionated heparin (UFH) in the treatment of acute coronary treatment are widely recognized. On the other hand, the need for continuous intravenous infusion and rigorous monitoring of its anticoagulant effect, among others, are downsides to its utilization. Low molecular weight heparins (LMWHs) are drugs whose anticoagulant effect is similar to that of UFH, but they are easier to administer (SC) and do not require laboratory monitoring. They have differences in chemical, pharmacologic and clinical characteristics. When we compare three of the most commonly used LMWHs – enoxaparin, dalteparin e nadroparin – we notice they differ from pharmacological and clinical points of view. In double-blind studies conducted in acute coronary syndromes, dalteparin and fraxiparin proved to be superior to placebo and equivalent to UFH, but only enoxaparin proved to have superior efficacy when compared to UFH, and extending its benefit for a prolonged period (one year after discharge). Therefore, although belonging to the same class of compounds, LMWHs cannot be viewed as “equivalent” drugs.